1. Field of the Invention
The present invention relates generally to a detection plate having a chip module arranged in or on an antenna module, and more specifically to such a detection plate in which a coupling loop of the chip module is inductively coupled to an antenna conductor of the antenna module.
2. Description of the Related Art
A data carrier having an electronic chip which can be read, and optionally written, remotely by a reader is termed a detection chip. It obtains the energy required for its chip from the reader without contact. Both the transmission of data and the transmission of energy take place by means of an electromagnetic field.
Where detection plates are used for the identification of persons, they can be the size of a credit card. For the detection of objects, smaller sizes may be necessary.
In the case of detection plates operating at a frequency in the LF or HF range, it is not possible to realize antennas adjusted mechanically to half-wave. It is only possible to achieve antenna resonance by the use of concentrated components. For this reason, the antenna is most commonly designed as an antenna coil of an oscillating circuit. In the case of detection plates operating at a frequency in the UHF and SHF ranges, however, it is possible to realize dipole antennas with half-wave dimensions, or at least dipole antennas which are mechanically shortened but electrically lengthened.
In any case, dipole antennas are sensitive to neighboring objects. Objects with dielectric conductance can lead to a detuning of the antenna resonance frequency. Electrically conductive objects, particularly metal objects, can absorb energy, act as shields, or likewise lead to a detuning of the antenna resonance frequency.